1. Field of the Invention
The present invention relates to an information display device comprising an information display panel enables to repeatedly display information such as an image accompanied by flight and movement of particles utilizing Coulomb's force and so on, and particularly relates to an information display device in which a contrast ratio after endurance can be improved.
2. Description of Related Art
As an information display device substitutable for liquid crystal display (LCD), information display devices with the use of technology such as an electro-phoresis method, an electro-chromic method, a thermal method, dichroic-particles-rotary method are proposed.
As for these information display devices, it is conceivable as inexpensive visual display device of the next generation from a merit having wide field of vision close to normal printed matter, having smaller consumption with LCD, or having a memory function, and spreading out to a display for portable device and an electronic paper is expected. Recently, electrophoresis method is proposed that microencapsulate dispersion liquid made up with dispersion particles and coloration solution and dispose the liquid between faced substrates, and also it is expected.
However, in the electrophoresis method, there is a problem that a response rate is slow by the reason of viscosity resistance because the particles migrate among the electrophoresis solution. Further, there is a problem of lacking imaging repetition stability, because particles with high specific gravity of titanium oxide is scattered within solution of low specific gravity, it is easy to subside, difficult to maintain a stability of dispersion state. Even in the case of microencapsulating, cell size is diminished to a microcapsule level in order to make it hard to appear, however, an essential problem was not overcome at all.
Besides the electrophoresis method using behavior in the solution, recently, a method wherein electro-conductive particles and a charge transport layer are installed in a part of the substrate without using solution is proposed. [The Imaging Society of Japan “Japan Hardcopy '99” (Jul. 21-23, 1999) Transaction Pages 249-252] However, the structure becomes complicated because the charge transport layer and further a charge generation layer are to be arranged. In addition, it is difficult to constantly dissipate charges from the electro-conductive particles, and thus there is a drawback on the lack of stability.
As one method for overcoming the various problems mentioned above, an information display device comprising an information display panel is known, in which at least one group of particles are sealed in a plurality of cells formed by partition walls between the opposed substrates, at least one of two substrates being transparent, and, in which the particles, to which an electrostatic field is applied by utilizing electrodes arranged to the substrates respectively, are made to move so as to display information such as an image.
In the information display device mentioned above, for example, a transparent conductive material such as ITO formed on a surface of the substrate such as glass substrate is patterned to be a line shape for example so as to form an electrode, and then partition walls are formed thereon by means of a photo-resist method to make a plurality of cells, in which at least one group of the particles are sealed. In this cases, since a gap like a valley is formed between adjacent electrodes on the substrate, in the case such that a particle diameter D of the particles is small with respect to a height H of the electrode (height between a surface of the substrate and an upper surface of the electrode), the particles spilled from a gap between opposed electrodes are caught in the gap between the electrodes and do not move, and thus a display defect sometimes occurs. This problem occurs in the same manner for the information display device comprising the information display panel, in which at least one group of particles are sealed in a plurality of cells formed by partition walls between the opposed substrates, at least one of two substrates being transparent, and, in which the particles, to which an electrostatic field is applied by utilizing electrodes arranged to the substrates respectively, are made to move so as to display information such as an image.